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issues after carb rebuild and sync.

  • Thread starter Thread starter cloud624
  • Start date Start date
C

cloud624

Guest
I just rebuilt my carbs and replaced air boots + carb boots. After syncing the carbs I took it for a run and after a couple minutes the throttle failed to give power. The bike sounded groggy with a deep gurgle type of noise with no power as I pulled the throttle back and eventually died several times on the way home. I do have a r/r issue that's pending full diagnosis but don't see how that would cause this type of issue. I checked the fuel, throttle, choke and vacuum cables and they are connected properly. All boots are tightly installed and I also weatherstripped both covers of the air box.

Someone mentioned that it could be a leak in my vacuum hose but that's set correctly with no indication of a leak. i also have a quarter tank of gas in the bike which rules out a fuel issue.

Any ideas of what might be going on? I'm kind of lost at this point.

btw this is my first bike and my first time rebuilding carbs. Im following directions to a T (trying to) and can't thank everyone on this site enough for their guidance.
 
cloud624 said:
...i also have a quarter tank of gas in the bike which rules out a fuel issue.
Click to expand...

Maybe.... maybe not.

On some bikes, a quarter tank will be below the fuel pick-up on the petcock. Try putting it on "reserve", or even simpler, fill the tank up with gasoline. That may solve your "problem".
 
You could also check and make sure that the gas cap is venting. It only takes a couple screws out to find out. Spiders love it under there.

V
 
Could be a petcock problem. Could also be a problem with the vacuum port to the petcock. I've also seen the fuel line get kinked causing fuel starvation. Sometimes hard to see with the tank on. Make sure your fuel line isn't too long. If everything ran fine until a couple minutes running, then that could very well be one of the above issues. Try running it with the petcock in the prime position first. Run it with the gas cap loose as well.
 
I agree with the others that you might just be running out of gas, but this also caught my eye:
cloud624 said:
I do have a r/r issue that's pending full diagnosis but don't see how that would cause this type of issue.
Click to expand...
Depending on your type of R/R issue, you might be running out of spark, too.

.
 
Like JTGS850GL said, petcock sounds quite possible.
Sounds like it let's gas out fast enough to keep up at idle but under load on the road it's just trickling in the bowls going below the pickup height for the main jet.
Test the petcock.
1- unplug the main fuel line and vaccuum line from the petcock.
2 - put a temporary 1 ' piece of vaccuum hose and 3' peice of fuel line (or anything) on the petcock.
3- put the 3' (supply line) hose in a clear container and suck with constant vaccuum on the vaccuum hose.
4- a medium stream of fuel should come out. Fast enough to fill let's say a 12oz pop can in about 30 seconds. (Others here have posted other ways to measure the flow rate out of the petcock). My pop can method was just off the top of my head.
It should be a medium flow....not a thin stream or just dripping.

Sorry if that was a obvious description of a simple test.
 
londonboards said:
Just take some float bowl drain plugs out and see if there is fuel in the float bowls.
Click to expand...

The only problem with that suggestion is that, by the time you get off the bike and pull the float bowl plugs, the bowls would be likely be filled again if it's a slow filler.
 
Thank you guys. I should've also stated that my petcock is most certainly malfunctioning. If you will moves through the petcock into a generic fuel switch which was installed by the previous owner. I turned it on when I ride in turn it off when I'm parked. I usually ride with it on reserve but it will leak fuel slowly while on prime.

Additionally below is a video of my engine warming up with the choke enabled. You will hear the RPM move up and down. I was told this could be an air leak but I'm unsure of how that could be since I weatherstripped the airbox and installed new air boots. On a separate note there's also a knocking/rattling noise that is coming from the crank case which is concerning. (Sorry if I ran off and a tangent) I think I've run into every issue possible but I'm determined to get this bike back in shape!

https://youtu.be/cvtFQHg7eaA


Either way I'll be troubleshooting while keeping your suggestions of mind!


Appreciate everyone's input.
 
Well there are also the carb intake boots on the engine side of the carbs. They have rubber o rings behind them that will shrink and crack making an air leak you cannot see. Rising and falling slowly is not as much of an air leak issue as is racing to high rpm's is. Not sure if an air leak is your problem.
You certainly have a noise going on. I think it's time you remove the valve cover gasket, do a valve adjustment and check your cam chain tightness and guides when you take the cover off. Your cam chain tensioner may be stuck or out of adjustment. Your cam chain guides may new be worn or broken.
Bike cliffs site has maintenance procedures to check and repair all these items. As does the factory service manual which is there for free also.
Do a valve adjustment anyways. Check all cam related items while you have the top off.
Don't mess with the cam chain adjuster until you read up on it.
You are in store for some real maintenance and evaluation of you want a really dependable bike you will look forward to riding instead of worrying about.
It's worth it.
 
Last edited:
gustovh said:
You could also check and make sure that the gas cap is venting. It only takes a couple screws out to find out. Spiders love it under there.

V
Click to expand...
I watched Vince disassemble a gas cap in a motel parking lot because it was spitting gas... Try that.
 
I'm not sure which carbs you have but I've found that for many people just finishing a rebuild the problem is either vacuum or vent. On many CV carbed bikes there are 2 tubes that need to vent under the seat near the battery. Petite hate to leave lets open and often end up attaching them together thinking they are part if the vacuum system. The symptoms seen similar.
 
Had a mud dauber take up residence in the vent tubs once, was fun finding that out.

V
 
Had one cylinder not firing... Turned out to be a spider that took up residence inside the pilot air jet while the carbs sat on my bench for a couple months.
 
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